It is now generally accepted that there is a close relationship between the development of colorectal cancer and pre-existing adenomas of the colon. Identification and removal of these adenomas have been associated with a reduced risk for colorectal cancer. Non-removal of adenomas has been associated with an increased risk for colorectal cancer. Current concepts indicate the advisability of close surveillance of this population with endoscopic and radiologic techniques to clear the colon of synchronous and metachronous adenomas to reduce the patient's risk for colorectal cancer. However, the frequency of examination, the yield for each examination, the risk to the patient, and the cost of such a program are not known. In addition, the survival benefit of such a program has not been established, although it is based on rational positions. The purpose of the present program is to determine the benefit, risks and costs of a surveillance program in patients at risk for colorectal cancer by virtue of a pre-existing adenoma that has been removed, and to further determine the proper interval of examination and the type of examination which would give the patient the best configuration of benefit and risk for future colorectal cancer. Patient compliance with these programs will be evaluated. The data provided by this study would allow recommendations to be made for general application of radiological and endoscopic and biochemical methods in the surveillance of patients at risk for colorectal cancer by virtue of a pre-existing adenoma that has been removed. The important aspects of cost will be identified and risks determined. If these factors can be established and recommendations be made for widespread use of this surveillance program in these high-risk patients, there could be a very significant impact made on future incidence of colorectal neoplasia in this high-risk population. These recommendation could provide a rational basis for cancer control in this high risk group of patients who have had an adenoma identified and removed.